A heat sink assembly includes a heat sink (10), a fan cover (20) mounted on the heat sink and a fan (30) carried by the fan cover. The heat sink comprises a base (12) and a plurality of spaced heat dissipation fins (140) extending from the base. The spaced heat dissipation fins define a plurality of channels (16) extending through front and rear ends of the heat sink. A cavity (40) is formed between the front end of the heat sink and the fan cover. The front end of the heat sink is configured with an arced front edge or an inclined front edge.